1. Technical Field
The present disclosure relates to a distortion-compensating power amplifier and a method for compensating for signal nonlinear distortion resulting from power amplification, by performing pre-distortion.
2. Description of the Related Art
In recent years, mobile equipment including, for example mobile phones and notebook computers equipped with wireless communication functions, is becoming increasingly widely used. In wireless communication devices provided in mobile equipment, adjacent-channel leakage power increases owing to nonlinear input/output characteristics of power amplifiers. The power amplifiers require high linearity for the input/output characteristics.
For example, in order for mobile equipment using a millimeter wave band to receive large amounts of data of moving images or to deliver different large amounts of data to respective users in parallel, adjacent channels are assigned to the users. When the adjacent-channel leakage power increases, interference with the adjacent channels increases.
It is, however, difficult to achieve a high power output and a high efficiency while maintaining high linearity, and it is desired to apply a nonlinear distortion compensation technique. As a system for compensating for nonlinear distortion in power amplifiers, a pre-distortion system has attracted attention in recent years. The pre-distortion system is a method in which an inverse characteristic of a distortion characteristic that is generated in a power amplifier is given to an input signal in advance and the resulting signal is then input to the power amplifier (see, for example, Japanese Unexamined Patent Application Publication No. 2005-79935 (hereinafter referred to as “Patent Document 1”) and Summary in Japanese Unexamined Patent Application Publication No. 2000-99022 (hereinafter referred to as “Patent Document 2”)).